1. Field of the Invention
This invention relates to an audio signal output device, and more particularly to an audio signal output device having audio signal output terminals of a plurality of channels and a common terminal provided therefor.
2. Description of the Related Art
The audio signal output devices of this kind include, for example, a stereo output device which is disposed on the output side of a video tape recorder (VTR) or an audio tape recorder.
In the devices of this kind in general, noises are generated when a reproduced output is in an unstable state or when the mode of operation of the recorder changes. To solve this problem, practice has been to mute such noises by causing a short circuit between each audio signal output terminal and a common terminal (common line) by means of a semiconductor switch or the like.
However, in the case of such a device, the semiconductor switch actually gives some on-state resistance when a short circuit between the audio signal output terminal and the common terminal is caused by turning on the semiconductor switch for the purpose of muting. Hence, the amount of output-signal attenuation attainable by carrying out the muting is determined by a ratio between a load connected to each output terminal, such as the impedance of a speaker or a headphone, and the above-stated on-state resistance of the semiconductor switch.
Where a sufficient amount of attenuation of the output is not attainable at the time of muting with the on-state resistance of the semiconductor switch being excessively large, it has been impossible to sufficiently subdue the noises generated within the recorder.